Compilare: main.cpp: In function 'Mult factor()': main.cpp:45:13: warning: array subscript has type 'char' [-Wchar-subscripts] m.v[s[i]] = 1, i++; ^ main.cpp: In function 'int main()': main.cpp:51:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i++) { ~~^~~~~~~~~~ main.cpp:53:17: warning: array subscript has type 'char' [-Wchar-subscripts] viz.v[s[i]] = 1; ^